Normally closed reed switch



@ct. 17, 1967 A. J. WILKIS 3,348,175

NORMALLY CLOSED REED SWITCH Filed April 26, 1966 INVENTOR. ANTHONY J.WILKIS ATTY.

United States Patent 3,348,175 NURMALLY CLUSED REED SWlTCH Anthony J.Wilkis, Downers Grove, 11]., assignor to Automatic ElectricLaboratories, Inc., Northlake, IlL, a corporation of Delaware 1 FiledApr. 26, 1966, Ser. No. 545,386 3 Claims. (Cl. 335-154) This inventionrelates to sealed reed switches and more particularly to reed switcheshaving a set of normally closed contacts.

Conventional break type reed switches usually are of basically make typedesign. That is, these switches comprise a pair of normally open reedsof magnetic material sealed into a glass capsule, but in addition, havea permanent magnet outside of the capsule for holding these normallyopen reeds in a normally closed position. Upon energization of a windingwound about the reed switch capsule, to produce a magnetic field, withpolarity opposite to, and magnitude greater than, that of the permanentmagnet, the reeds will be released from engagement.

U.S. Patent 2,922,856 discloses another example of a normally closedtype reed switch device, which comprises two reeds, one of magenticmaterial and the other of non-magnetic material, which extend into asealed glass tube, one from each end thereof, and whose inner, contactends are normally making contact with one another. Located inside theglass tube, near one end thereof, is an insulating member into which amagnetic element is mounted, in parallel, spaced relation to thenon-magnetic reed. Upon operation of the switch, the inner contact endof the magnetic reed is drawn to the free end of the above magneticelement, thereby breaking contact between the inner, contact ends of thetwo reeds.

The construction of the above-mentioned reed switch requires, inaddition to the usual mounting facilities for each of the two reeds, aseparate mounting for the magnetic element and its associated insulatingmember.

Accordingly, it is an object of this invention to provide an improvedbreak type reed switch device which does not require a magnet forbiasing the switch in its normally closed position.

It is a further object of this invention to provide an improved breaktype reed switch of basically make type design which can be easilyfabricated and economically produced.

The normally closed reed switch according to the principal feature ofthe present invention comprises a sealed envelope having two magneticreeds extending thereinto,

one from each end of the envelope, in spaced relation to each other. Oneof the reeds has insulating means covering its inner end, and near thisend there is attached a non-magnetic, metallic member whose free endnormally contacts the inner end of the other magnetic reed. When theswitch is energized, the two inner ends of the magnetic reeds are drawntogether breaking the above-mentioned connection, but because of thepresence of the insulating means, electrical contact is not made onewith the other.

Other objects and features of this invention will become more apparentby reference to the following description taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a side view of a preferred embodiment of a break type reedswitch according to the invention in its unoperated condition, and

FIG. 2 is a side view of the reed switch of FIG. 1 in its operatedcondition.

Referring to FIG. 1, a preferred embodiment of the reed switch accordingto the invention comprises an envelope of insulating material, such asglass, into which two magnetic reeds 11 and 12 extend from oppositeends. An energizing winding 17, wound about envelope 10, is provided foractuating the switch.' The reeds overlap and are normally spaced fromone another at their inner ends 14 and 16. Near the inner end 15 of oneof reed 11 there is attached by welding, or other suitable means, a Zshaped, non-magnetic, metallic member or spring 13 which normally makeselectrical and mechanical contact with the inner end 16 of the othermagnetic reed 12. Reed 11 also has on its inner end 14 a coating ofplastic insulating material, such as Teflon, to prevent electricalcontact between the two magnetic reeds upon operation of the reedswitch.

Upon energization of winding 17, the two inner ends 14 and 16 are drawntogether as shown in FIG. 2, breaking the electrical and mechanicalconnection between metallic member 13 and the inner end of magnetic reed12. As mentioned above, due to the coating of insulation on the innerend of reed 11, no electrical contact is made between the magnetic reedswhen they are drawn together. It is to be noted that, instead of coatingthe entire inner end of reed 11, it would be possible to merely coat theconfronting surfaces 1 8, 19 of one or both magnetic reeds 11 and 12.Also, insulating methods other than coating of the reed ends withplastic insulating material may be used. Also, actuation by magneticmeans other than energizing winding 17 may be employed.

Thus, the normally closed reed switch according to the inventionrequires no external permanent biasing magnet, and yet has a structuregenerally similar to that of a conventional make type reed switch,requiring, like the make type switch, only two mounting facilities, onefor each of the two magnetic reeds. Therefore, the normally closed reedswitch of the present invention is relatively simple to construct andeconomical to produce.

Due to the fact that no biasing magnet is used to hold the reed switchof the invention normally closed, there is no danger, as there is with abreak type switch biased by a permanent magnet, that the field of themagnet will cause false operations of make type contact switches thatmay be used along with the break type switch. Also, the reeds of theabove-mentioned break type switches which rely on permanent magnetbiasing tend to stick due to remanent magnetism unless special measuresare taken to prevent this. In contrast, the present constructioneliminates the danger of sticking upon energization by virtue of spring13 being of non-magnetic material, and upon release by virtue of thefact that the inner ends of magnetic reeds 11 and 12 are separated byinsulating material. By the same token, the thickness of the insulatinglayer may be used to control the release time of the reed switch ifdesired.

It will be obvious to those skilled in the art that changes andmodifications may be made without departing from this invention in itsbroadest aspects and therefore the aim in the appended claims is tocover all such changes and modifications as are within the true spiritand scope of this invention.

What is claimed is:

1. A reed switch comprising:

a sealed envelope of insulating material having first and secondmagnetic reeds extending thereinto with one surface of their respectiveinner ends facing each other in an overlapping, normally spacedrelation;

insulating means on said surface of the overlapping inner end of atleast one of said reeds;

a non-magnetic, metallic member secured to said first reed near saidinner end thereof, and bent to extend in spaced parallel relationship tosaid insulating means to normally make both mechanical and electricalcontact with the surface of the overlapping inner end of said secondreed opposite said one surface; and magnetic actuating means arrangedoutside said envelope and operative upon actuation to cause the innerends of said first and second reeds to be attracted towards one anotherto thereby break contact between said metallic member and the inner endof said second reed. 2. A reed switch as claimed in claim 1 wherein saidreeds extend into said sealed envelope from the opposite ends thereof,and wherein said non-magnetic, metallic member is substantially Z-shapedand is welded to said first reed.

References Cited UNITED STATES PATENTS 1/1960 Karrer 335154 8/1964 Ohkiet al. 335-154 X 1 BERNARD A. GILHEANY, Primary Examiner.

R. N. ENVALL, ]R., Assistant Examiner.

1. A REED SWITCH COMPRISING: A SEALED ENVELOPE OF INSULATING MATERIALHAVING FIRST AND SECOND MAGNETIC REEDS EXTENDING THEREINTO WITH ONESURFACE OF THEIR RESPECTIVE INNER ENDS FACING EACH OTHER IN ANOVERLAPPING, NORMALLY SPACED RELATION; INSULATING MEANS ON SAID SURFACEOF THE OVERLAPPING INNER END OF AT LEAST ONE OF SAID REEDS; ANON-MAGNETIC, METALLIC MEMBER SECURED TO SAID FIRST REED NEAR SAID INNEREND THEREOF, AND BENT TO EXTEND IN SPACED PARALLEL RELATIONSHIP TO SAIDINSULATING MEANS TO NORMALLY TAKE BOTH MECHANICAL AND ELECTRICAL CONTACTWITH THE SURFACE OF THE OVERLAPPING INNER END OF SAID SECOND REEDOPPOSITE SAID ONE SURFACE; AND MAGNETIC ACTUATING MEANS ARRANGED OUTSIDESAID ENVELOPE AND OPERATIVE UPON ACTUATION TO CAUSE THE INNER ENDS OFSAID FIRST AND SECOND REEDS TO BE ATTRACTED TOWARDS ONE ANOTHER TOTHEREBY BREAK CONTACT BETWEEN SAID METALLIC MEMBER AND THE INNER END OFSAID SECOND REED.